The LLVM integrated assembler doesn't support the extensive macro system that GNU as does. To implement the code without the heavy macros I wrote a C program to use C's macros to unroll all the code and printf each instruction to create interim files that were combined to make skein_block_asm.S that LLVM would compile. As looping would require the assembler to have the macro support it lacks all the loop code was removed. As the SKEIN_DEBUG code wasn't in use by FreeBSD I also removed it.
Tested with libmd's make test target